In general, in an electronic device including a mobile terminal for mobile communication, several input means are used. In a keypad for inputting a numeral or for selecting a menu, a numeral key and a navigation key are mounted; and, in addition to such keys, for user convenience, a side button or key is additionally provided to be exposed to the outside of the terminal.
The side button or key exposed to the outside of the terminal is connected to a main Printed Circuit Board (PCB) to be used for adjustment of a communication volume while communicating and for movement of a displayed menu.
For assembly of the side button or key in a housing of the electronic device, the housing was conventionally designed to form a slope between a gap of a product exterior and a gap within a key assembly by injection; however, nowadays, particularly for application of a metal case, a key hole should be processed at a side surface of the housing by a flat end mill processing instead of injection. In this case, the key hole is processed without a side wall slope; thus, the side key unit is assembled such that an outer edge gap of a key that forms an external appearance of a product maintains the same gap to the inside of the key assembly. Therefore, a micro gap is formed that enables a gap between the side key unit and the key hole to be maintained the same.
For example, when an outer edge gap is 0.03 mm, an internal gap may be maintained to 0.03 mm, and when a width direction thickness of the key housing is 1.3 mm, a width of a micro gap may be also 1.3 mm.
However, as importance of a design (external appearance quality) of the electronic device increases, a gap of a side key unit, side cover, or window has been reduced. However, in the side key unit as a driving body, a click impression of a key as well as management of a gap of an external appearance becomes a major element that enhances completeness of a product.
In such a situation, for a product quality, i.e., for gap management in relation to a key external appearance and movement prevention of a key, when the key gap is minimized, a micro gap is included between the side key unit and the housing. Accordingly, a foreign substance from daily life such as cosmetic, lotion, coffee, cold medicine, and cola may easily enter; the entered foreign substance may spread widely to a front surface of a gap portion of the key due to surface tension thereof; and, while the entered foreign substance becomes sequentially solidified (phenomenon in which viscosity increases), a frictional force increases and thus, when the key operates, an uncomfortable click impression is caused.
When a metal case is applied, if a processing step for improving a function is added in addition to a step of forming a key hole for assembling a key, the processing number increases; thus, a processing time and a unit cost may increase.